1. Field of the Invention
The present invention relates to a pneumatic tire having a sidewall part.
2. Background Information
In recent years, the thickness of the sidewalls (herein also referred to as “side gauge”) in pneumatic tires has been reduced in order to decrease weight and roll resistance. However, there is a high probability that the sidewall surface will have a poor appearance when the side gauge is reduced. This poor appearance does not negatively affect the durability or other kinematical performance of the tire, but does cause a user to worry whether the tire is defective and has poor durability or other kinematical performance problems.
When a tire is manufactured, a sheet-shaped carcass member is made to wrap around once on a tire-mold drum and the beginning edge and ending edge are joined with a portion overlapping in the molding step. For this reason, the overlapping portion becomes thicker, and this portion appears as an irregularity on the sidewall surface of the final tire. This irregularity is remarkably conspicuous, especially in radial tires in which a single carcass member is used.
A pneumatic tire that makes the irregularity that develops on the sidewall surface of the tire inconspicuous is described in Japanese Laid-open Patent Application No. 2011-37388. That is, a decorative part extending in a belt shape in a tire circumferential direction of the outer surface of the above pneumatic tire has formed thereon a first ridge group and a second ridge group comprising a plurality of ridges arranged so as to extend in a tire radial direction at a predetermined pitch. The irregularity existing on the sidewall surface can be made inconspicuous by a moire pattern formed by the intersection of each ridge of the first ridge group and each ridge of the second ridge group.